In U.S. Pat. No. 4,898,156, entitled "Suture Anchor"; U.S. Pat. No. 4,899,743, entitled "Suture Anchor Installation Tool"; U.S. Pat. No. 4,946,468, entitled "Suture Anchor and Suture Anchor Installation Tool"; U.S. Pat. No. 4,968,315, entitled "Suture Anchor and Suture Anchor Installation Tool"; U.S. Pat. No. 5,002,550, entitled "Suture Anchor Installation Tool"; U.S. Pat. No. 5,046,513, entitled "Method For Anchoring Suture To Bone"; and U.S. Pat. application Ser. No. 07/766,025, filed Sep. 26, 1991, entitled "Suture Anchor and Installation Tool", there are disclosed a variety of anchors for anchoring a portion of a piece of conventional suture in bone. The foregoing patents and patent application further disclose several installation tools for deploying the anchors disclosed therein. Complete details of the construction and operation of these suture anchors and installation tools are provided in the above-identified patents and patent application, which patents and patent application are hereby incorporated herein by reference.
It will, therefore, be understood that suture anchors of the sort comprising a coupling member and at least one elastically deformable, normally curved barb member extending outwardly from the coupling member are known in the art. It will also be understood that installation tools for deploying such suture anchors in holes formed in workpieces (e.g. bone) are similarly known in the art.
As the requirements of users of such devices have become more demanding, however, known suture anchors and known suture anchor installation tools have encountered several problems. More particularly, it has been found that there is a growing desire in the medical field to anchor suture to smaller and smaller bones, and hence to deploy smaller and smaller suture anchor in smaller and smaller holes formed in those bones.
Until now, however, two primary factors have tended to limit the extent to which it was possible to reduce the size of both the suture anchors and also the size of the anchor-receiving holes.
First, the suture anchor's coupling member, which forms the body of the anchor, must include sufficient material to ensure the structural integrity of the anchor. In addition, the suture anchor's coupling member must include means for attaching the suture to the anchor, and means for engaging the anchor with its associated insertion tool. At the same time, of course, the anchor-receiving holes must be formed large enough to accommodate the suture anchors therein. Thus, those factors which tend to limit the downsizing of suture anchor bodies also tend to limit the downsizing of anchor-receiving holes.
Secondly, known suture anchor installation tools are designed to operate so that the portion of the installation tool which engages and carries the anchor remains in engagement with the anchor the entire time that the anchor is moving to its desired location within the bone. With such prior art designs, the engaging and carrying portion of the installation tool separates from the anchor only after the anchor has been deployed in the bone. Thus, with prior art designs, the anchor-receiving holes must be formed large enough to receive not only the suture anchor but also the engaging and carrying portion of the installation tool as well.
Accordingly, while various suture anchor designs and installation tool designs have been disclosed in the aforementioned patents and patent application, including (a) the alternative of moving the suture attachment means from the distal end of the coupling member toward the proximal end of the coupling member so that the suture need not pass by the outside of the coupling member to reach the exterior of the bone, and hence the anchor-receiving hole can generally be formed somewhat smaller, and (b) the alternative of reducing the diameter of the proximal end of the coupling member relative to the remainder of the coupling member so that the proximal end of the coupling member can be received by an installation tool, while at the same time forming the installation tool so that it has an outside diameter no larger than the largest diameter of the coupling member, there are practical limits to the effectiveness of these prior art constructions as suture anchor sizes and bone hole sizes become smaller and smaller. Among other things, the attachment means for attaching the suture to the anchor generally requires the presence of sufficient coupling member material at the point of attachment to ensure that the suture will not break free from the coupling member. For example, if the attachment means comprises a hole formed in the reduced diameter proximal portion of the coupling member, it will be appreciated that the diameter of the reduced diameter proximal portion of the coupling member must always significantly exceed the diameter of the suture so as to ensure proper structural integrity. Similarly, as long as that portion of the insertion tool which engages and carries the suture anchor must also enter the bone hole so as to move the suture anchor to its desired location in the bone, there are practical limits as to how small the insertion tool's shaft may be formed without creating problems in mounting the suture anchor to the installation tool, and without creating bending problems in the shaft when driving suture anchors into bone.